Fix flaky append regression test take 2

In timescale#7512 we added manual `VACUUM` in all involved relations to avoid
flaky output tests.

But looks like it is not working very well specially on Windows builds,
so now we're replacing the output `Heap Fetches: [0-9]` for `Heap
Fetches: 0` to make have a more predictable output test.

test/runner_cleanup_output.sh

@@ -8,7 +8,8 @@ RUNNER=${1:-""}
 sed  -e '/<exclude_from_test>/,/<\/exclude_from_test>/d' \
      -e 's! Memory: [0-9]\{1,\}kB!!' \
      -e 's! Memory Usage: [0-9]\{1,\}kB!!' \
-     -e 's! Average  Peak Memory: [0-9]\{1,\}kB!!' | \
+     -e 's! Average  Peak Memory: [0-9]\{1,\}kB!!' \
+     -e 's! Heap Fetches: [0-9]\{1,\}! Heap Fetches: 0!' | \
 grep -v 'DEBUG:  rehashing catalog cache id' | \
 grep -v 'DEBUG:  compacted fsync request queue from' | \
 grep -v 'DEBUG:  creating and filling new WAL file' | \